llvm/clang/test/CXX/class/class.compare/class.rel/p1.cpp

// RUN: %clang_cc1 -std=c++2a -verify %s

struct Good {
  int operator<=>(const Good&) const;

  bool operator<(const Good&) const = default;
  bool operator>(const Good&) const = default;
  friend bool operator<=(const Good&, const Good&) = default;
  friend bool operator>=(const Good&, const Good&) = default;
};

enum Bool : bool {};
struct Bad {
  bool &operator<(const Bad&) const = default; // expected-error {{return type for defaulted relational comparison operator must be 'bool', not 'bool &'}}
  const bool operator>(const Bad&) const = default; // expected-error {{return type for defaulted relational comparison operator must be 'bool', not 'const bool'}}
  friend Bool operator<=(const Bad&, const Bad&) = default; // expected-error {{return type for defaulted relational comparison operator must be 'bool', not 'Bool'}}
  friend int operator>=(const Bad&, const Bad&) = default; // expected-error {{return type for defaulted relational comparison operator must be 'bool', not 'int'}}
};

template<typename T> struct Ugly {
  T operator<(const Ugly&) const = default; // expected-error {{return type}}
  T operator>(const Ugly&) const = default; // expected-error {{return type}}
  friend T operator<=(const Ugly&, const Ugly&) = default; // expected-error {{return type}}
  friend T operator>=(const Ugly&, const Ugly&) = default; // expected-error {{return type}}
};
template struct Ugly<bool>;
template struct Ugly<int>; // expected-note {{in instantiation of}}